<template>
  <div>
    <p>请选择你要购买的书籍</p>
    <ul>
      <li v-for="(obj,index) in arr" :key="index">
        {{obj.name}} <button @click="buybook(index)">买书</button>
      </li>
    </ul>
    <table border="1" width="500" cellspacing="0">
      <tr>
        <th>序号</th>
        <th>书名</th>
        <th>单价</th>
        <th>数量</th>
        <th>合计</th>
      </tr>
      <tr v-for="(obj,index) in arr " :key="index" >

        <td>{{index+1}}</td>
        <td>{{obj.name}}</td>
        <td>{{obj.price}}</td>
        <td>{{obj.count}}</td>
        <td>{{obj.price*obj.count}}</td>
      </tr>
    </table>
    <p>总价格为:{{sum}} </p>
  </div>
</template>

<script>
export default {
  data () {
    return {
      arr: [
        {
          name: '水浒传',
          price: 107,
          count: 0
        },
        {
          name: '西游记',
          price: 192,
          count: 0
        },
        {
          name: '三国演义',
          price: 219,
          count: 0
        },
        {
          name: '红楼梦',
          price: 178,
          count: 0
        }
      ]
    }
  },
  methods: {
    buybook (ind) {
      this.arr[ind].count++
    }
  },
  computed: {
    sum () {
      return this.arr.reduce((sum, item) => (sum += (item.price * item.count)), 0)
    }
  }

}
</script>
